BMW X3 3 5 E60 E61 E83 E87 E90 1 Fuel Tank Filler Cap Cover DIESEL 7786331

BMW X3 3 5 E60 E61 E83 E87 E90 1 Fuel Tank Filler Cap Cover DIESEL is an original component from the Fuel filler flaps and caps group, designed for BMW diesel systems. It ensures a tight seal of the filler neck, stabilizes the fuel system operation, and helps maintain proper operating conditions for the diesel engine in the rear section of the vehicle.

Specifications and technical data

• SKU: 7786331-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7786331
• Substitutable numbers: 7786331, 71227786331, EM
• Location on the vehicle: Rear
• Fuel type: Diesel
• Category: Fuel Tank Caps

Purpose and technical function

The presented cap is dedicated to BMW vehicles with diesel engines where the fuel filler is located in the rear part of the body. Its task is to maintain controlled pressure in the tank, limit fuel evaporation, and effectively protect the system from external contaminants.

Thanks to a design matched to factory filler sockets, this component works with the original filler pipe and outer cover, which translates into a secure closure and predictable behavior of the fuel system in daily operation.

Compatibility and fit for BMW

The cap has been designed with specific BMW models in mind, which means maintaining the correct geometry, diameter, and mounting method. Such a fit minimizes the risk of leaks, looseness, or problems with closing the fuel filler flap.

The original BMW origin helps maintain consistency with other body and fuel system components – both in terms of technical and visual aspects. This is particularly important in vehicles where compliance with factory specifications and predictable behavior during refueling are essential.

Performance characteristics of the Diesel cap

As a component intended for Diesel fuel, the cap is adapted to the specifics of diesel oil, including its chemical properties and operating conditions in the fuel system. The design ensures:

• a stable closure of the filler in the rear of the vehicle,
• protection against the ingress of water, dust, and other contaminants,
• maintenance of proper conditions for the operation of the diesel fuel system.

Such a solution helps reduce the risk of starting problems, uneven engine operation, or errors related to the fuel system resulting from filler leaks.

Condition, origin, and benefits of installation

The component comes from disassembly, which allows for maintaining factory specifications while reducing repair costs compared to new parts. Choosing an original cap from the secondary market is often a favorable compromise between price and maintaining compliance with the manufacturer's solutions.

A properly selected fuel filler cap from this component group facilitates installation because it uses factory mounting points and the standard method of operation during refueling. As a result, the replacement is usually quick, and the driver retains the familiar way of opening and closing the filler.

Expanding knowledge about the fuel system

To better understand the role of the filler cap in the entire supply system, it is worth familiarizing yourself with material discussing the operation of injectors, pumps, and the fuel tank – this is described in detail in the article Fuel system – injectors, pumps, and fuel tank: maintenance and regeneration, where you will find practical tips regarding diagnostics and operation.

If you are planning a comprehensive repair or upgrade of the fuel filler area in your BMW and need other elements from the same group, such as flaps, hinges, or seals, check the available parts in the BMW fuel filler flaps and caps category.